The document describes the thyroid gland and its hormones. It discusses the morphology of the thyroid gland, located in the neck, as having two lobes and an isthmus. The gland contains follicles that produce the hormones thyroxine (T4) and triiodothyronine (T3). It also discusses the higher control of the hypothalamus and pituitary gland on the thyroid. The main hormones produced are T4, T3, and thyrocalcitonin. These hormones impact growth, metabolism, and other bodily functions.

1. INTRODUCTION
TO THYROID HORMONE
FARRA NAJWA BINTI ABDUL AZIM
082015100035

2. LEARNING OBJECTIVES
AT THE END OF THE SEMINAR, STUDENTS SHOULD BE ABLE TO :
• DESCRIBE THE MORPHOLOGY OF THYROID GLAND
• DESCRIBE THE HIGHER LEVEL OF CONTROL
• LIST THE HORMONES PRODUCED BY THE THYROID GLAND
• UNDERSTAND THE FUNCTION OF THYROID HORMONES

3. MORPHOLOGY OF THYROID GLAND
• Largest gland (15 – 25 gm)
• Located at in inferior of thyroid cartilage
• Butterfly in shape
• Two lobes ; left and right ; isthmus
• Microscopic of thyroid follicles and C cells
• T4 and T3 present in colloid bound to large
protein -> thyroglobulin

4. HIGHER LEVEL OF CONTROL
Hypothalamus
Releasing & Inhibiting Hormones
Blood Vessels (Median Eminence)
Hypothalamo-hypophyseal Portal
Vessels
Anterior Pituitary

5. HIGHER LEVEL OF CONTROL
Releasing hormones:
1. Thyrotropin-releasing hormone (TRH)
2. Corticotropin-releasing hormone (CRH)
3. Growth hormone-releasing hormone (GHRH)
4. Gonadotropin-releasing hormone (GnRH)
5. Prolactin-releasing hormone (TRH)

6. HYPOTHALAMIC – PITUITARY AXIS

7. HORMONES
• Thyroid hormones are essential for normal growth of tissue and also
stimulates basal metabolic rate.
• Consists of :
• Thyroxine (T4)
• 2 tyrosines + 4 bound iodine atoms
• Triiodothyronine (T3)
• Main hormone secreted
• By follicular cells
• Amino acid derivaties ( tyrosine )
• 2 tyrosines + 3 bound iodine atoms
• Thyrocalcitonin
• By parafollicular cells – C cells

8. HORMONES
• Synthesis of T4 and T3 are stimulated by :
• Increase of thyroid stimulating hormone (TSH)
• Synthesis of T4 and T3 are reduced by:
• Decrease in thyroid stimulating hormone (TSH)
• Glucocorticoid, dopamine and somatostatin
• Normal TSH level is 0.5-5 microunits per ml.
• Low TSH level leads to hypothyroidism
• High TSH level leads to hyperthyroidism

9. FUNCTIONS

10. FUNCTIONS
• BRAIN – Development of nervous system
• BONE & TISSUE – Linear growth, maturation of bones
• CVS – Increases contractility, heart rate, cardiac output
• GUT – Increase absorption of nutrients, motility
• LIVER – increase glucogenesis & glycogenolysis
• ADIPOSE TISSUE – Increased lipolysis
• MUSCLE – Increase protein catabolism
• KIDNEY – Increase erythropoietin
• RESPIRATION – Increase central stimulation
• ENERGY METABOLISM – Increase BMR, oxygen consumption, heat
production stimulation of Na-K-ATPase

11. SUMMARY
• SHAPE, SIZE
• LOCATION
• MICROSCOPIC
• LOBES
MORPHOLOGY
• HYPOTHALAMUS
• PITUITARY GLAND
• HYPOTHALAMO – PITUITARY AXIS
HIGHER LEVEL OF
CONTROL
• THYROXINE (T4)
• TRIIODOTHYROXINE (T3)
• THYROCALCITONIN
HORMONES
• METABOLIC FUNCTION
• GROWTH
• BUILDING OF BONE
• USE OF GLUCOSE FOR ATP PRODUCTION
FUNCTIONS

12. REFERENCE
• TEXTBOOK OF BIOCHEMISTRY FOR MEDICAL STUDENTS, DM
VASUDEVAN, 6TH EDITION